1. Field of the Invention
This invention generally relates to a linear motion guide unit, and, in particular, to a linear motion guide unit manufactured from a resin at least partly.
2. Description of the Prior Art
A linear motion guide unit is well known and it generally includes a rail extending straight over a desired length, a slider which is slidably mounted on the rail and a plurality of rolling members interposed between the rail and the slider to thereby provide a rolling contact between the slider and the rail. Such a linear motion guide unit has a wide range of applications.
Typically, such a linear motion guide unit is manufactured from steel or a sheet metal partly because of the required structural strength. However, in some applications, the weight of such a linear motion guide unit plays a predominant role and thus it is not uncommon that such a linear motion guide unit is required to be very light in weight. In addition, as the range of applications expand, the size of such a linear motion guide unit is often desired to be very small.
In order to meet such requirements, it is often desired to manufacture such a linear motion guide unit from a resin material. However, partly because of the difficulty in using a resin material in some of the components of such a linear motion guide unit, the use of a resin material in manufacturing a linear motion guide unit has been rather limited. For example, there has been proposed to fabricate a slider or a part thereof from a resin material; however, there has nor been proposed to fabricate a rail of a linear motion guide unit from a resin material. Since the rail can be a dominant factor in determining the overall weight of such a linear motion guide unit, it is crucial that such a rail can be fabricated from a resin material in really making a light weight unit. In addition, if the entire or major portion of such a linear motion guide unit can be manufactured from a resin material, its manufacture can be extremely facilitated, which could also contribute to lower the manufacturing cost.
In a typical prior art linear motion guide unit, since most of its components are fabricated from a metallic material, such as steel, the overall weight has to become relatively large and separate fastening means, such as bolts or rivets, must be used to assemble the unit. Thus, the manufacture of such a prior art linear motion guide unit tends to be complicated and thus high in cost. In addition, such a typical prior art linear motion guide unit manufactured from a metallic material tends to be limited in applications since it necessarily creates noises and requires lubrication. Moreover, such a prior art unit cannot be used in some corrosive or magnetic environment.